Optical units are known per se, they are used inter alia in camera systems, and developers of such systems constantly strive to obtain smaller, lighter, thinner, better and cheaper camera systems. From International application WO 2004/027880 in the name of the present applicant, for example, there is known a camera system comprising an image capturing element, a lens element for projecting an object onto the image capturing element, a spacer for maintaining a predetermined distance between the lens element and the image capturing element, whilst furthermore a lens substrate is provided, on which the lens is disposed. From U.S. Pat. No. 6,985,307 there is furthermore known a lens assembly, according to which the optical length, which is defined as the distance from the object side of the imaging lens to the image-forming surface of a CCD or the like, must be short. Such a lens is often referred to as a compact lens, and in a mobile telephone, for example, the optical length must at least be shorter than the thickness of the telephone itself. The lens must furthermore be configured so that the image obtained with such a lens is visually acceptable. U.S. Pat. No. 6,985,307 thus provides a lens assembly made up of a first lens, a second lens and a third lens, of which lenses special requirements are made as regards the curvature, the distance between the lenses and the thickness of the lenses that are used. From International application WO 2008/01103 there is furthermore known a camera system comprising three substrate layers, on which five optical elements are formed.
The camera modules used in mobile telephones require more and more resolution and optical functionalities, and that within increasingly smaller dimensions. Thus, new lens systems must be developed, comprising lenses having a greater sag height, sometimes referred to as deeper lenses, which lenses must exhibit at least the same dimensional precision as the previously produced lenses. The present applicant has found that, using the current production methods, considerable efforts are required to realize the intended shape or dimensional precision in the increasingly deep lenses.
Thus it is an object of the present invention to provide an optical unit in which it is possible to realize the required shape precision of the lens system without this leading to undesirably increased dimensions of the optical unit.